TECHNICAL SPECIFICATION
2. SPECIFIC TECHNICAL REQUIREMENTS
Sl.No. Particulars 33/11 KV Power Transformer
1 Rated MVA (ONAN rating) 5MVA & 10 MVA
2 Number of Phases Three
3 Vector group Dyn-11
4 Type of installation Outdoor
5 Frequency 50HZ ( +/- )5%
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6 Cooling Medium Insulating Oil (ONAN)
7 Type of Cooling ONAN (Oil natural / Air natural)
8 MVA Rating corresponding to ONAN 100%
9 Rated Voltage :-
High Voltage winding 33kV
Low Voltage winding 11kV
10 Highest continuous system voltage a) Maximum system voltage ratio (HV /
LV )
36.3KV / 12 KV
b) Rated voltage ratio (HV / LV ) 33KV /11 KV
11 Winding Material Electrolytic Copper
12 Winding Connection :-
High Voltage Winding DELTA
Low Voltage Winding STAR
13 Vector group reference Dyn11
14 No. of windings Two winding Transformers
15 Method of System Earthing Solidly grounded on LV side 16 Neutral terminal to be brought out On LV side only
17 Core Material CRGO ( M-4 / higher grade)
18 Core Assembly Boltless type
19 Type of Tap Changer On-load tap changer (OLTC)
20 Range of Tapping + 5% to – 15% in 17 equal steps of 1.25%
each on HV winding 21 Intended regular cyclic overloading of
windings
As per IEC –76-1, Clause 4.2
22 a) Anticipated unbalanced loading Around 10%
b) Anticipated continuous loading of windings (HV / LV)
110 % of rated current
23 Over Voltage operating capability and duration
112.5 % of rated voltage (continuous)
24 Withstand time for three phase short circuit
2 Seconds
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25 Maximum current density for HV andLV winding for rated current
2.4 Amp/ Sq.mm.
26 Maximum flux density in any part of the core and yoke at rated MVA, rated voltage
i.e 33kV / 11kV and system frequency of 50 Hz
1.55 Tesla
27 Maximum Flux Density in any part of the core and yoke at 112.5 % of rated voltage i.e 33 KV /11 KV and system frequency of 50 HZ
1.9 Tesla
28 Insulation 33kV 11kV
a) Type of insulation Uniform Uniform
b) One minute power frequency withstand Voltage(kV rms)
29 Nominal short circuit level (Basing on apparent power)
31.5KA 25KA
30 Insulation level of bushing
a) Lightning Impulse withstand (KVP) 170 75 b) 1 Minute Power Frequency withstand
voltage (KV –rms )
70 28
31 Minimum clearances in air (mm) Phase to Phase
Phase to ground
a) HV 400 320
b) LV 280 140
32 c) Creepage distance (mm) (minimum) 972 324 33 Percentage impedance voltage on
normal tap and MVA base at 75o C corresponding to HV/ LV rating and applicable tolerances: (No negative
34 Permissible Temperature Rise over ambient temperature of 40 / 45˚C
a) Of top oil measured by thermometer 40˚C b) Of winding measured by resistance 45˚ C
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35 Noise level at rated voltage andfrequency
As per NEMA Publication No. TR-1
36 Terminal Details
a) HV winding line end 36 KV oil filled communicating type porcelain bushings (Anti-fog type) b) LV winding 17.5 KV porcelain type of bushing (Anti-fog
type) 37 Polarization index
(HV to LV, HV to Earth & LV to earth)
IR Test = 1 minute value/ 15 secs. value will not be less than 1.5
IR Test = 10 minutes value / 1 minute value will not be more than 5 and less than 1.5
38 Temperature Indicator
a) Oil (SCADA compatible) One number b) Winding (SCADA compatible) One number
39 33kV Termination Terminal connector of HV and LV shall be vertical take off type and suitable for ACSR Panther
11 KV Termination
40 Type of mounting On Wheels, Mounted on rails.
Terminals
(11KV Power cables shall be used for extending supply to 11KV breakers in case of indoor circuit breakers. The termination of 11 KV cables on LV bushing shall be through extended copper bus bars suitable to hold power cables termination. A metallic cable termination box, completely sealed, shall be installed on LV side of the transformer in which cables shall enter from bottom gland plates.) 41. Losses:- The losses shall not exceed the value given below
MVA Rating No-load
The above mentioned losses are maximum permissible and there shall not be any plus tolerance above this limit.
The bidder shall submit design calculation of No load and Load losses along with complete technical details and factors assumed along with the GTP in tender documents. In case during testing, the actual losses are found within guaranteed figure, the transformers shall be accepted without any advantage to the bidder for lower losses. Measurement of losses shall form part of type test/routine test. The purchaser reserves the right to reject the transformers if on testing, the losses exceed the declared losses or the temperature rise in oil and/or winding exceeds the value guaranteed in technical particular or impedance
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value differ from the guaranteed value and if any test results do not match with the values given in the guaranteed technical particulars and as per technical specification2.1 MARSHALLING BOX
A metal enclosed, weather, vermin and dust proof marshalling box fitted with required glands, locks, glass door, terminal Board, heater with switch, illumination lamp with switch etc. shall be provided with each transformer to accommodate temperature indicators, terminal blocks etc. It shall have degree of protection of IP 55 or better as per IS: 2147
2.2 CAPITALIZATION OF LOSSES AND LIQUIDATED DAMAGES Not applicable for bid evaluation purpose.
2.3 PERFORMANCE
i) Transformer shall be capable of withstanding for two seconds without damage to any external short circuit, with the short circuit MVA available at the terminals.
ii) The maximum flux density in any part of the core and yoke at rated MVA. Voltage and frequency shall be 1.55 Tesla (maximum).
iii) Transformer shall under exceptional circumstances due to sudden disconnection of the load, be capable of operating at the voltage approximately 25% above normal rated voltage for a period of not exceeding one minute and 40% above normal for a period of 5 seconds.
iv)The transformer may be operated continuously without danger on any particular tapping at the rated MVA± 1.25% of the voltage corresponding to the tapping.
v) The thermal ability to withstand short circuit shall be demonstrated by calculation.
vi)Transformer shall be capable of withstanding thermal and mechanical stress caused by any symmetrical and asymmetrical faults on any winding.
2.4 DRAWINGS/ DOCUMENTS INCORPORATING THE FOLLOWING PARTICULARS SHALL BE SUBMITTED WITH THE BID
a) General outline drawing showing shipping dimensions and overall dimensions, net weights and shipping weights, quality of insulating oil, spacing of wheels in either direction of motion, location of coolers, marshalling box and tap changers etc.
b) Assembly drawings of core, windings etc. and weights of main components / parts.
c) Height of center line on HV and LV connectors of transformers from the rail top level.
d) Dimensions of the largest part to be transported.
e) GA drawings / details of various types of bushing f) Tap changing and Name Plate diagram
g) Type test certificates of similar transformers.
h) Illustrative & descriptive literature of the Transformer.
i) Maintenance and Operating Instructions.
2.5 MISCELLANEOUS
i) Padlocks along with duplicate keys as asked for various valves, marshalling box etc. shall be supplied by the contractor, wherever locking arrangement is provided.
ii) Foundation bolts for wheel locking devices of Transformer shall be supplied by the Contractor.
2.6 DELIVERY
The full quantity of the equipments shall be delivered as per the delivery schedule appended to this specification.
2.7 SCHEDULES
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All Schedules annexed to the specification shall be duly filled by the bidder separately.2.8 ALTITUDE FACTOR
If the equipment is to be installed in the hilly area, necessary correction factors as given in the Indian Standard for oil temperature rise, insulation level etc. shall be applied to the Standard Technical Parameters given above.
2.9 NAME PLATE
Transformer rating plate shall contain the information as given in clause 15 of IS-2026 (part-I).
The details on rating plate shall be finalized during the detailed engineering. Further, each transformer shall have inscription of Employer‟s name. The name plate shall also include (i) The short circuit rating , (ii) Measured no load current and no load losses at rated voltage and rated frequency, (iii) measured load losses at 75° C ( normal tap only ), (iv) D.C resistance of each winding at 75° C.